Production of polyisopropyl benzene



i not used asa ffeed stock.,

PRODUCTION FV POLYIS'OPROPYL BENZENE Albert .l. Shmidl, Crosby, Tex., assigner, by mesne asv`Signmnts, to Esso Research and Engineering Company, Elizabeth, NJ., a corporation of Delaware Filed June 6, 1958, Ser. No. 740,280

9 claims. (c1. 26o- 6711) The present invention is directed to a method for producing polyalkylated benzene. More particularly, the

vinvention is directed to a method for producing polyisopropyl benzene. In its most specific aspects, .the inventioii is `"doncerned with producing 1,3,5 Yt-rlflsopropyl benzene and' l,2,4,5 tetra-isopropyl benzene.

The present invention may be. briefly described as a:

method for producing polyalkylatedbenzene -by form-` ing a reaction mixture of propylene and an aromatic hyfdrocarbon seleeted fromthe group consisting of benzene and isopropyl .benzene and thereafter contactmg the nuxture with .a silica-alumina catalyst atla temperature the 'range from labout 5300"' to about 450 F. for arsuicient length of time to form a product containing a substantialamounto'f 1,3,5 tri-isopropylene and .thereafter recovering the product. Y

It is contemplated that the; lrecovered product,tri z isopropylene, may :be used as such but preferably is ormed into a solution in .a liquid saturated aliphatic Y hydrocarbon having a boil-ing point diiferent from that voi the tri-isopropylene and then ysubjected toalkylation with additional amounts ofpropylene. This latter alkylation with I'propylene causes the formation of the l,2,4,5 tetraisopropylene and is conducted at a temperature within the range from about I60 to about 80 F. with a sulfuric acid catalyst having `a strength within the range from about 85%.to about 92%v H2804. The product formed is a result of the s eomd valkylation step.l It is distilled to separate the solvent and unreacted trifisoproptyl benzene and to recover the tetra-,isopropyl benzene which thenrmay be .subjected t0 crystallizationto purify further the tetrafifsnopropylabenzene, The solvent and unreacted tti-isopropylene may be .recycledV to the second alkylation stage. f

It is important ithat-the yfeedl stock be benzene or isopropyl benzene (cumene) since the normal propyl benzene does not react satisfactorily to form the tri-.isopropyl benzenedesired, A Therefore, normal propyl benzene 1s The propylene and. the benzene or cumene are used in amounts of about 2 molar Avolumes of propylene per molar volume of the benzene or cumene. Satisfactory alkylation to form the desired tri-isopropyl benzene is obtained with 'a ratio of propylene to'beuzene or cumene of about 2 to about 4 molar volumes. Y The reaction may be' represented by theequation:

The of propylene yand benzene or cumene is "contacted with thel silica-alumina catalyst at the aforesaid temperatures fora time within the range from about 15 to `about 60V minutes. *Stating this otherwise, a space 4.0.v.`/v./hr. maybe used.`

velocity in the range fromabout 0.5 v./v./hr. to about l I. l l

v kthereby into a fractional dlstlllatlon zone 19 Villustrated not crystallize :from the solvent. -propyl benzene hasa freezingpoint of `242 F. and will .Aflow diagramU'o-f a preferred fmode.

ICC,

The :Itri-*isopropyl -ben-zeneformed as an intermediate reaction :product has a freezing .point of 5 F. and will However, 4tetra-isocrystall-ize readily at alkylation temperatures of about v to about 80 'F. and, therefore, :in practicing the present invention it is important that the tri-isopropyl benzene lbe .dissolved -in .a vsuitable solvent .prior to further alkylation suoh'that the tetra-isopropyl benzene will not terystallize at alkylation temperatures.

The solvents should be a liquid saturated aliphatic hydrocarbon having a. boiling point .different from that of the triisopropylbenzene and different from that of the Ytetra-sopropyl benzene to allow ready separation thereof.

contain f,a small amount of tri-isopropyl benzene. Therefore, it is desirable in the Ypractice .of the present invention to Verystallize the tetra-isopropyl benzene from solutionand ;to.achie1ve this end a solvent such as one .of

the natureadescribed may be employed to crystallize the .tetrad'sopropyl benzene from the solution. this crystallization, the separated tetra-isopropyl benzene To achieve .is put in .solution in a solvent of the nature described and the temperature adjusted to a temperature in' the range between about. 80 F to about -40 F. to cause the tetra-isopropyl benzene to crystallize and to allolw recovery of'th'e separated crystals.

The amount of solvent added to the tri-isopropyl ben-V zene may be in the range `fromY about 1 to about 5.0 volumes vof solvent per volume of tri-isopropyl benzene. This amount of solvent will maintain the tetra-isopropyl benzene product in solution. Likewise, the amount of solvent added to `purify the tetra-isopropyl benzene may be in the range :from about l to about 5.0 volumes per volume of tetra-isopropyl benzene. i

-It is important that a Vsilica-alumina catalyst be employed in the rst stage to cause the selective formation of tri-isopropyl benzene for ready separation from the monoand di-isopr'opyl ben'zenewhich may be formed or from thernonodsopropyl ben-zene as unreact-ed feed when cumene is a feedstock. With respect to the sulviuric: aeidwcatalyst employed vlin the second stage operation, it Ais importantlthat acids having the strength spe ciedjbeernployedsince with higher! strength acids cousiderable amounts of lcoke and slu'dgy material are formed whereas with lower strength acid -very little,'if any, alkylation proceeds. Y

NThe present'invention will' be further illustarted by Yreference to the 'drawing in which the single figure is a Referring now `to the drawing, numeral 111 designates a charge line by way of which propylene and benzene or cumene is introduced into a furnace 12. provided with a heating coil 12oy and supplied with heat from gas burners 14. As a result of the feed mixture passing through the coil 13 the temperatureis adjusted to Va temperature in the range from about 300 to yabout 450 F., and the heated product at a pressure 'in the range from about 400 to about .5.00 Vp.s.i.g. isintroduced by way of line 415 into Aa reaction zone 16 :provided with a bed of silica-alumina catalyst 17. On passage of fthe heated feed stock through the` bed 1-7 a product. is formed containingsubstantial quantities of ithe.- particular. ltr'i-isoln'opylene desired.v This product as a single distillation tower provided with a heating means' 'and cooling means, means for, inducing reux,' and the like.

Zone 19 is operated under conditions to discharge by way of line 22. any light products' which may Ihave been `formed in zone 16 and to discharge by way of line 22 monoand di-isopropyl benzene While the desired porduct,

Vpentane and tri-isopropyl benzene solution to be pumped tri-isopropyl benzene, is withdrawn'from zone`19 by Y way of line 23. The monoand cli-isopropyl benzene may be withdrawn from the system'by opening valve Z4 in line 22 but preferably are recycledlto line 11 through line 25 controlled by valve Z6 which introduces .the monoand di-isopropylene into line 11 in admixture with the propylene. Line 2.7 controlled by valve 28 discharges `into line 25 for introduction of fresh benzene or curnene into the system. Y

The tri-isopropylene in line Z3 may bewithdrawn as a product by way of line Z9 controlled by valve 30 but preferably is introduced by way of line 23, by opening valve 31, into la second alkylation system or stage which will be described further hereinafter.

Since the tri-isopropyl benzene solidies readily at atmospheric temperatures a solvent of the nature described is introduced into line Z3 by line 32 to form a solution of the tri-isopropyl benzene. Into this solution there is introduced by way of line 33 a sucient amount of propylene for alkylation with the tri-isopropyl benzene. The amount of propylene employed in the second'alkylation stage may range from about y1 molar volume of propylene -per molar volume of the .tri-isopropyl benzene. Also introduced into the solution by way of line 34 is a sulfuric acid catalysthaving a strength from about 85 to about 92% H2804. The solution of pentane and tri-isopropyl benzene to which the acid and propylene have been added is then `discharged into -line 35 through la mixing zone 36 which is illustrated as a centrifugal pump but which may be any mixing device such as an incorporator, a countercurrent mixing tower, a stirred agitator or any mixing apparatus which will cause intimate admixture among the solution, the propylene, andthe acid catalyst.

The mixture of catalyst and solution is then discharged by way of line 37 into a settling zone 38 which is of sufficient capacity to provide a suflicient residence time to allow a separation between the alkylated product and the acid catalyst. A separation is thus Vmade in zone 38 and the separated acid catalyst is withdrawn by line 39 and preferably is recycled at least-in part by way of line 40 controlled by valve 41 and containing pump 42 to line 34 for recycling through zone 36.

From time to time it will be desirable to discard part of the acid in line 39 and this may be done by opening valve 43. When acid is discarded from line 39, as has been described, it will be desirable and necessary to add make-up acid of the proper strength and this may suitably be accomplished by opening valve 44 in line 34 connected to a source of acid of the required strength to maintain the 85 to 92% H2804 acid strength in the second alkylation stage.

The alkylated product is withdrawn from zone 38 by line 45 and introduced thereby into a second distillation zone 46 which is similar in all respects to zone 19 and is provided with a heating means such as a steam coil Y auxiliary A(solvent. and unreacted tri-isopropyl benzene from the tetra-isopropyl benzene. The pentane solvent may be taken oli as a separate stream by way of line 48 and the tri-isopropyl benzene also may be withdrawn as a separate stream by way of line 49 controlled by valve 50. isopropyl benzene are withdrawn as a combined stream by way of line 48, valve 50 in line 49 being closed and valve 5-1 in line48 being opened, connecting line 48 with recycle line 52 controlled by valve 53, allowing the by pump 54 toline 32 -for admixing with the solution in line 23. It will be understood, of course, that valve 55 in line 48vwill remain colsed during these operations. It is also to be understood that, rather than tri-isopropyl benzene being withdrawn by line 49, the solution of pentane and tri-isopropyl benzene may be withdrawn by line 49 with valve 51 remaining closed.

The substantially purified tetra-isopropyl benzene is discharged from zone 46 by line 56 and may be taken olf Aas product by opening valve 57. Preferably, however,

`valve 57 is maintained closed and valve 58 in line 59 Vis opened, discharging the tetraisopropyl benzene which may contain some tri-isopropyl benzene into a crystallization zone 60 after admixture with solvent introduced by line 61 controlled by valve 62.

Temperature conditions are adjusted in zone 60 to cause precipitation of the tetra-isopropyl benzene as crystals from the solution and to 4allow discharge of the crystals 'from zone 60 by line 63 with the supernatant liquor `being discharged Aby way of the line 64. While pentane `is described as the solvent for the tetra-isopropyl benzene, 'isopropyl alcohol may be used. Su'cient solvent may be used to provide a saturated solution at 160 F. Then by lowering the temperature to within the range from about V to about 0 F., tetra-isopropyl benzene will crystallize and may be recovered in purity of 99% by centrifuging.

Since some of the pentane or other solvent may be lost in the operation, line 32 is provided with a valve 65 for introduction of make-up pentane solvent into the system.

From the foregoing description taken with the drawing, it will be seen that a new and improved method has been provided for forming polyalkylated benzene and, specifically, triand tetra-isopropyl benzene.

The present invention is of considerable importance and utility in that the particular benzenes formed in this operation are quite useful as solvents, the tri-isopropyl benzene being substantially odorless and, therefore, quite attractive for this use. The tri- "and tetra-isopropyl benzenes are also useful for manufacture of chemicals.

'I'he nature and objects of thepresent invention hav-ing been completely described and illustrated, what I wish to claim as new and useful and to secure by Letters Patent is:

1. A method for producing a polyalkylated benzene which comprises Iforming a reaction mixture of propylene and an aromatic hydrocarbon selected from the group. consisting of benzene and isopropyl benzene in a ratio of propylene to aromatic hydrocarbon in the range from about 2 to about 4 molar volumes per volume, contacting said mixture with a silica-alumina catalyst at a temperature within the range from about 300 to about 450 F. for a sufcientlength of time to form a product containing a substantial amount of 1,3,5 tri-isopropyl benzene, distilling said product to recover said tri-isopropyl benzene, forming a solution of said tri-isopropyl benzene in a liquid saturated aliphatic hydrocarbon having a boiling point different from that of the tri-isopropyl benzene, adding an alkylation amount of propylene at least l molar volume of propylene per molar volume of tri-'isopropyl benzene to said solution, contacting the propylene-containing solution at a temperature within the range from about 60 toabout 80 F. with a sulfuric acid catalyst having a strength with-inthe range from about% to about 92% H2894 to form a product containing a substantial amount Preferably, however, the pentane solvent and tri-l of 1,2,4,5 tetra-isopropyl benzene and recovering substantially puritied 1,2,4,5 tetra-isopropyl benzene from said product.

2. A method for producing a polyalkylated benzene which comprises forming a reaction mixture of propylene and an aromatic hydrocarbon selected from the group consisting of benzene and lisopropyl benzene in a ratio of propylene to aromatic hydrocarbon in the range from about 2 to about 4- molar volumes per volume, contacting said mixture with a silica-alumina catalyst at a temperature within the range from about 300 to about 450 F. for a suicient length of time to form a product containing a substantial amount of 1,3,5 triaisopropyl benzene, distilling said product to recover said tri-isopropyl benzene, forming a solution of said tri-isopropyl benzene in a saturated aliphatic hydrocarbon having 5 to 7 carbon atoms and having a boiling point different from that of the tri-isopropyl benzene, adding an alkylation amount of propylene at least 1 molar volume of propylene per molar volume of tri-isopropyl benzene to said solution, contacting the propylene-containing solution at a temperature within the range from about 60 to labout 80 F. with a sulfuric acid catalyst having a strength Within the range from about 85% to about 92% H2804 to form a product containing a substantial amount of l,2,4,5 tetra-isopropyl benzene and distilling said product to recover substantially purified 1,2,4,5 tetra-isopropyl benzene.

3. A method for producing a polyalkylated benzene which comprises forming a reaction mixture of propylene and an aromatic hydrocarbon selected from the. group 30 consisting of benzene and isopropyl benzene in a ratio of propylene to aromatic hydrocarbon in the range from about 2 to about 4 molar volumes per volume, contacting said mixture with a silica-alumina catalyst at a temperature Within the range from about 300 to about 450 F. for a sufficient length of time to form a product containing a substanttial amount of 1,3,5 tri-isopropyl benzene, distilling said product to recover said tri-isopropyl benzene, forming a solution of said tri-isopropyl benzene in pentane, adding an alkylation amount of propylene at least 1 molar volume of propylene per molar volume of tri-isopropyl benzene to said solution, contacting the propylene-containing solution at a temperature Within the range vfrom about 60 to about 80 F. with a sulfuric acid catalyst having a strength within the range from about 85% to about 92% H2504 to form a product containing a substantial amount of 1,2,4,5 tetra-isopropyl benzene, distilling said product to recover substantially purified 1,2,4,5 tetra-isopropyl benzene and said pentane and unreacted tri-isopropyl benzene, and admixing at least a portion of the recovered pentane and unreacted tri-isopropyl benzene with said solution.

4. A method lfor producing a polyalkylated benzene which comprises forming a reaction mixture of propylene and an aromatic hydrocarbon selected from the group consisting of benzene and isopropyl benzene in a ratio of propylene to aromatic hydrocarbon in the range from about 2 to about 4 molar volumes per volume, contacting said mixture with a silica-alumina catalyst at a temperature within the range from about 300 to about 450 F. for a sucient length of time to form a product containing a substantial amount of 1,3,5 tri-isopropyl benzene, `distilling said product to recover said tri-isopropyl benzene, forming a solution of said tri-isopropyl benzene in a liquid saturated aliphatic hydrocarbon having a boiling point different from that of the tri-isopropyl benzene, adding an alkylation amount of propylene at least 1 molar volume of propylene per molar volume ofY triisopropyl benzene to said solution, contacting the propylene-containing solution at a temperature within the range from about 60 to about 80 F. with a sulfuric acid catalyst having a strength within the range from about 85% to about 92% H2804 to form a product containing a subl5` stanti'al amount of l,2,4,5 tetra-isopropyl benzene, distilling said product to recover said tetra-isopropyl benzene, and then crystallizing said recovered tetra-isopropyl benzene to obtain 99% purity 1,2,4,5 tetra-isopropyl benzene.

5. A method for producing a polyalklated benzene which comprises forming a solution of 1,3,5 tri-isopropyl benzene in a liquid saturated aliphatic hydrocarbon havn ing a boiling point different from that of the tri-isopropyl benzene, adding an alkylation amount of propylene at least 1 molar volume of propylene per molar volume of tri-isopropyl benzene to said solution, contacting the propylene-containing solution at a temperature Within the range from about 60 to about 80 F. with Va sulfuric acid catalyst having a strength within the range from about 85% to about 92% H2SO4 to form a product containing a substantial amount of 1,2,4,5 tetra-isopropyl benzene,-

and recovering substantially purified 1,2,4,5 tetra-isopropyl benzene from said product.

6. A method in accordance with claim 5 in which the saturated aliphatic hydrocarbon has 5 to 7 carbon atoms.

7. A method in accordance with claim 5 in which the saturated aliphatic hydrocarbon is pentane.

8. A method in accordance with claim 5 in which the product is recovered by distillation.

9. A method in accordance with claim 5 in which the product is recovered by distillation followed by crystallization.

References Cited in the iile of this patent UNITED STATES PATENTS 2,848,514 DeKeizer et al. Aug. 19, 1958 FOREIGN PATENTS 323,100 Great Britain Dec. 24, 1929 763,181 Great Britain Dec. 12, 1956 OTHER REFERENCES 

1. A METHOD FOR PRODUCING A POLYALKYLATED BENZENE WHICH COMPRISES FORMING A REACTION MIXTURE OF PROPYLENE AND AN AROMATIC HYDROCARBON SELECTED FROM THE GROUP CONSISTING OF BENZENE AND ISOPROPYL BENZENE IN A RATIO OF PROPYLENE TO AROMATIC HYDROCARBON IN THE RANGE FROM ABOUT 2 TO ABOUT 4 MOLAR VOLUMES PER VOLUMES, CONTACTING SAID MIXTURE WITH A SILICA-ALUMINA CATALYST AT A TEMPERATURE TURE WITHIN THE RANGE FROM ABOUT 300* TO ABOUT 450*F. FOR A SUFFICIENT LENGTH OF TIME TO FORM A PRODUCT CONTAINING A SUBSTANTIALLY AMOUNT OF 1,3,5 TRI-ISOPROPYL BENZENE DISTILLING SAID PRODUCT TO RECOVER SAID TRI-ISOPROPYL BENZENE, FORMING A SOLUTION OF SAID TRI-ISOPROPYL BENZENE IN A LIQUID SATURATED ALIPHATIC HYDROCARBON HAVING A BOILING POINT DIFFERENT FROM THAT OF THE TRI-ISOPROPYL BENZENE, ADDING AN ALKYLATION AMOUNT OF PROPYLENE AT LEAST 1 MOLAR VOLUME OF PROPYLENE PER MOLAR VOLUME OF TRI-ISOPROPYL BENZENE TO SAID SOLUTION, CONTACTING THE PROPYLENE-CONTAINING SOLUTION AT A TEMPERATURE WITHIN THE RANGE FROM ABOUT 60* TO ABOUT 80*F. WITH A SULFURIC ACID CATALYST HAVING A STRENGTH WITHIN THE RANGE FROM ABOUT 85% TO ABOUT 92% H2SO4 TO FORM A PRODUCT CONTAINING A SUBSTANTIALLY AMOUNT OF 1,2,4,5 TETRA-ISOPROPYL BENZENE AND RECOVERING SUBSTANTIALLY PURIFIED 1,2,4,5 TETRA-ISOPROPYL BENZENE FROM SAID PRODUCT. 